A biased look at psychology in the world

February 21, 2013

How Did REM Sleep Originate?

An article recently published in Dreaming presents a new theory about the origin of Rapid Eye Movement (REM) sleep. REM is
an integral part of the human sleep cycle and the neurological
substrate most consistently associated with dreams and dream recall.
According to this thesis, REM sleep evolved out of a primordial
defensive reflex: tonic immobility. This reflex, sometimes also called
death-feigning or animal hypnosis, is usually the last line of defense
against an attacking predator. Tonic immobility, common in both
vertebrates and invertebrates, has a number of neuroanatomical and
behavioral attributes that overlap with those of REM sleep. This overlap
is suggestive of an evolutionary kinship. The article presents
conceptual arguments and empirical facts in support of this
relationship.